Hello thank you lucky1 for your answer,
I found the problem ...
On this model of DMD it takes a voltage of 3.3v and not 5v
I did a test between 3.3 and 4.0v max everything is ok both DMD are powered correctly.
I am going today to give you my activation key via a Paypal payment;)

Hello everyone,
I just received my two DMD 160 * 80 identical to the post.
the voltage at 4.96v allows me to see the last two letters MD (of PIN2DMD) with the end of the activation key.
But the resolution is very big here is the result ...
the STM32F40 card works well under windows 10 and USB driver ok
Knowing that I tested with the firmware 2.64 / 2.65 and 2.66
same problem.
Do you have an idea ?
I have post my problem on : https://www.pincabpassion.net/t10701-en-cours-probleme-d-affichage-rectangles-de-couleurs-sur-le-dmd-160x80#184384
it's strange when I plug a single DMD to 3.3v the display is correct .... but at 3.3v the connection of the two DMD power cuts and black screen on both DMD.